Kavalahti Camping Site (Björnvikintie 109, 10230 Inkoon as), Inkoo, Finland. About an hour from Helsinki by car, and 90 minutes from Turku. There is also public transportation that comes rather close (busses on the Route 51, train to Karjaa).
The site has drinkable tab water inside and proper toilets. There are showers in the saunas. There are also two small kitchens for those, who want to cook for themselves.
The event is mainly a camp, groups may ask indoor sleeping possibilities by email. Please notive that COVID-19 can bring some changes to this.
The site rules bedsheets are mandatory for all sleeping in the beds, even if one uses a sleeping bag.
Unfortunately the site is a camping site, which can be challenging for people with reduced mobility. There is a toilet for disabled persons near the kitchen building, but moving around the camp is not accessible.